I am not familiar with this specific amp. But you have two routes you could go:
1. Find an exact replacement as suggested by Mike
2. If the amp has a signal send and return, you could used an external reverb unit. For external units, you have the choice digital units (not the pedal units though -- those are meant to be in between the guitar & the amp) or spring reverb units. There are lots of manufacturers for the digital reverb/delay units. Only a handful of people make the external reverb tanks like Uncle Spot Amps, Fender (I think they still do), etc.
